Evolution - Unit 2 Bio 11

What factors can affect an organism’s chances to survive?

Sever weather, famine, and competition for food, space, and mates are all challenges that organisms may or may not be able to survive. Organisms may adapt to their habitat and gain special features that help them survive.

Adaptation:

The result of gradual, accumulative changes that help an organism survive and reproduce.

Variation:

1. Structural

2. Functional,

3. Physiological

differences between individuals. They help an organism survive and reproduce in that particular environment. Changes are a result of random, heritable mutations in DNA accumulated over multiple generations.

ALL adaptations are variations, but NOT ALL variations are adaptations.

How are variations passed down?

• Variations that are advantageous are typically passed down to next gen through reproduction

• Variations that reduce chances of survival are rarely passed down

• Some cases variation may not have a negative effect on the survival or reproductive success of an organism, but may not provide and advantage either

Structural adaptations:

Physical features of an organism like a bill on a bird or the fur on a bear.

Mimicry:

Specific structural adaptation where an organism that would be considered harmless resembles a dangerous species in colour and/or structure.

Ex. Elephant Hawk Moth, Rubber fly, Mimic Octu

Camouflage:

Specific structural adaptation where an organism’s appearance (either colouration or structure) helps it blend in with its environment.

Ex. Leaftailed - Gecko, Orchid Mantis

Behavioural adaptations:

The things organisms do to survive.

Ex. Bird calls, migration

Physiological:

Internal, automatic body processes or chemical functions that enhances an organism’s survival.

Ex. Venom that snakes & spiders produce to

Hibernation:

Reduce their metabolism to save energy, to survive climates with harsh winters.

How does variation account for survival?

When there is a lot of genetic variation within a population we will be able to see the population evolve with their environment allowing for survival.

What can cause variation?

• Physical trauma

• Genetics (blood, eye/hair colour, earlobe shape)

• Environmental causes (Hair colour, language, scars, tattoos)

How does mutations create genetic variation?

Often result of UV rays damaging DNA. Can be harmful or beneficial to the survival of an organism or have no effect on survival.

Selective Advantage:

If a trait becomes an advantage. Antibiotic-resistant bacteria. Mutation that yields a resistance to a particular antibiotic. Resistance passed onto offspring via asexual reproduction. Therefore produce a population of antibiotic resistance bacteria.

English Peppered Moths:

Before Industrial revolution there were three colour variations white with black spots, black and intermediate colour.

Mid 1800s rare for black colored moths (2%). Trees were light-colored meaning light colored were well camouflaged.

Soot covered tress in late 1800s by 1900s black pop was estimated 95%

Artificial Selection:

Describes changes to a population caused by deliberate selective breeding by humans. Done in order to improve or modify particular desirable traits. These traits aren’t necessarily traits that would increase a populations fitness to survive in the wild.

Dogs:

These domestic animals have had traits artificially selected for a variety of different purposes over centuries. Led to lots of variety

All dogs carry same kinds of genes, so careful selection is done over many gen.

Consequences of Artificial Selection:

• English bulldogs are bred for different traits like their flat faces but trait results in respiratory problems

• German shepherds and other large dog breeds are prone to hip dysplasia and arthritis

• Plants will lack genetic diveristy (monoculture) meaning if they are so similar new disease can effect entire population

Food - Crops:

Things like rice, corn, wheat, and vegetables are the result of selective breeding.

Ex. Wild mustard plant been modified by selective breeding to create vegetable like broccoli, Brussels sprouts and cauliflower. Started over 4000 years ago in Europe and Asia.

Since they are members of same species they can interbreed and create things like broccoflower

Food - Animals:

• Cows that produce more milk

• Varieties of chicken are bred to grow rapidly and have large muscles for increased amounts of meat

• Other chicken are bred to produce more eggs

We can breed food crops to:

1. Increase nutritional yield

2. Be drought resistant

3. Be pest resistant

Can’t breed them to:

Grow too quickly as they might not be able to tolerate poor soil conditions, need variation to tolerate environmental changes

Preventative measures:

To combat disasters, gene banks have been established.

• Gene banks contain populations of early ancestors of modern plants

• specimen have been collected from the wild and from prehistoric archeological sites

• Genetic diversity can be introduced into modern planter if need arises

Evolution

The change in the heritable characteristics of biological populations over successive generations

Carl Linneaus: (1707 - 1778)

• Father of taxonomy, developed the naming and classifying system for the diversity of life

• Binomial nomenclature, e.g. Homo Sapiens

• Kingdom -> Phylum -> Class -> Order -> Genus -> Species - >

• Grouped living things based on physical similarities

• Provided the initial basis for deducing evolutionary relationships

Georges Cuvier: (1769 - 1832):

• Founded paleontology (study of fossils)

• As he explored down through each stratum (layer of rock) sedimentary rock, flora and fauna became more unlike current species

• This meant that new species appeared and others disappeared over the passage of time. This proved that species could become extinct

• Discovered proof of mass extinctions from floods and volcanic eruptions

• Proposed theory of Catastrophism, a series of major catastrophic events systematically wiped species out and new foreign species would re-populate

Charles Lyell: (1797 - 1875)

• Geologist who rejected Cuvier’s theories.

• He believed geological processes operated at the same rate throughout history as they do today in a process called uniformitarianism

• He believed that changes were slow and continuous, like the forces which build and erode mountains

• In order for this to be true the Earth had to be older than the biblical 4400 years

Jean-Baptiste Lamarck: (1744 - 1829)

• Proposed life was driven towards greater diversity and greater complexity

• Made observations about current species of animals and made comparisons to fossil records. Observed a progression in which a series of fossils led to a modern species

• Wrongfully proposed that characteristics acquired in a lifetime could be inherited

• Called the idea the “inheritance of acquired characteristics”. 

• If a giraffe stretched its neck for leaves, a nervous fluid would flow into its neck making it longer. Offspring would inherit the longer neck and continue stretching making it longer over future generations

Charles Robert Darwin: (1809 - 1882)

• English naturalist who went on a 5 year voyage abroad the HMS Beagle

• Many of his famous observations took place in and around the Galapagos islands off the coast of Ecuador

• It was not until years later did Darwin use his observations to develop his theory of evolution by natural selection

• Individuals with traits that helped them survive in their local environments were more likely to survive to pass on these traits to offspring

• Competition for limited resources between individuals with favourable traits (better for surviving and reproducing, AKA “survival of the fittest”

• Believed all life descended from an unknown organism

• Its descendants spread out over different habitats during the millenia, they developed adaptations that helped them better survive in their local environment.

Darwin Key Points:

1. Organisms produce more offspring than can survive, therefore organisms compete for limited resources

1. Individuals of a population vary extensively, and much of this variation is heritable

2. Individuals that are better suited to local conditions survive to produce more offspring

3. Processes for change are slow and gradual

Origins of Species:

• When Darwin first published The Origin of Species, he based his findings on his observations regarding the distribution of organisms throughout the world. He wasn’t the only person to conclude that life had changed over time, but he was the first to publish his ideas.

• Scientists from varying backgrounds (geologists, geographers, biologists,) provided plenty of evidence from their individual fields that also supported the theory of evolution by natural selection.

The Fossil Record:

• Provides a chronological record of organisms present throughout evolutionary history

• Sedimentary rock contains fossils and provides a fossil record of the history of living things on Earth.

• The age of the fossils can be approximated based on the depth of the fossil within the rock

Are there any problems with the fossil record?

1. Soft tissue of organisms does not form fossils

2. Some fossils are yet to be found

3. Fossils may be damaged/destroyed

4. Conditions not correct for fossil formation

5. Fossils may only be fragments/not whole organisms

Not all organisms appear in the fossil record at the same time:

• The fossil history of vertebrates shows that fish are the oldest vertebrates

• In subsequent layers, the fossils of other vertebrates - amphibians, reptiles, mammals, and birds appear.

• Reinforces scientific evidence that amphibians evolved from ancestral fish, reptiles evolved from ancestral amphibians, and both mammals and birds evolved from different groups of reptiles

Transitional Fossils:

• Fossils that show intermediary links between groups of organisms

• They help scientists better understand the evolutionary process

• Basilosaurus and Dorudon were ancient whales that had tiny hind limbs but led an entirely aquatic life. Dorudon was about the size of a large dolphin and had a tiny pelvis with legs measuring about 10 cm.

Radiometric Dating:

• Determines age of both rock and fossil remains. 

• Fossils were identified as mineralized remains or traces of organisms that are now extinct. The ability to measure relative amount of  parent and daughter in rock provide an accurate and reliable method of determining the age of both rock and fossil

Radioisotopes:

• Atoms with an unstable nuclear arrangement that decays and changes the atom into a different atom

• Carbon-14 has a half-life of 5730 yrs. This is the time it takes for 50% of C14 to become the daughter isotope N14. The half life for isotopes are constant over time and therefore can be used as naturally occurring clocks.

Biographical Evidence:

• Fossils of the same species can be found on the coastline of neighbouring continents. The present day location of the continents is not the same as it was historically. 

• About 510 million years ago, the continents of Africa and South America were joined in one supercontinent, Pangea.

• Biography studies the distribution of plants and animals worldwide

• Darwin discovered fossilized remains of tropical forests in the mountains. Fossilized sea specimens also found in the mountains.

• Darwin believed this was evidence that Earth’s environment had undergone continuous and dramatic change.

Comparative Anatomy:

• Despite their different functions, all vertebrate forelimbs contain the same set of bones organized in a similar function

• The most plausible explanation for this is that the basic vertebrate forelimb originated with a common ancestor

Homologous Features:

• Homologous structures are anatomical structures that have similar structure elements and origin but may have a different function

• Organisms have anatomical similarities when they are closely related because of common descent

Analogous Features:

• Body parts that perform similar functions, even though the organisms do not have a close common evolutionary origin, are called these structures

• Are inherited from unique ancestors and have come to resemble each other because they serve a similar function. Ex. Wings of birds & butterflies

Comparative Embryology:

• Study of early, pre-birth stages of an organism’s development

• Embryos of different organisms exhibit similar stages of embryonic development

• For example, all vertebrate embryos have paired pouches, or out-pocketings, of pouches become parts of the ears and throat, also during development, all vertebrates have a post-aal tail.

Vestigial Structures:

• Serve no useful function in a living organism

• Are homologous to fully functioning structures in closely related species

1. Pelvic bones and rudimentary leg bones in some pythons and boas

2. Appendix in humans

3. Rudimentary wings in many flightless insects

4. 2 of the 4 digits in pigs

Molecular Biology:

• Almost all living organisms use the same basic biochemical molecules e.g. DNA, ATP, enzymes

• Organisms utilize the same DNA triplet code and the same 20 amino acids in their proteins

• Similarities could be explained by common ancestors. Life’s vast diversity has come about by only a slight different in the same genes

T.Rex and Chickens share a common ancestor?

• After excavating a T. Rex fossil in 2003, scientists found it was too big to transport by helicopter. They carefully broke the thigh bone in half to ship it

• Results of later tests of the broken bone were surprising as it held preserved soft tissues

• These tissues included connective tissues, blood vessels, and possibly blood cells

• Two independent tests on the soft tissue indicate the T.rec is likely related to the present-day chicken (similar amino acid sequences). 

• Supports the theory that a common ancestor links birds to dinosaurs